Stability of Fermi liquid with respect to dynamical fluctuations in strongly correlated electron systems

Abstract: We solve quantum impurity models by means of the perturbation expansion in interaction strength. We derive a simplified form of the parquet equations justified in the strong coupling regime and low temperatures. Resulting numerically manageable computational scheme is applied to both the single impurity Anderson model and the infinite-dimensional Hubbard model. We obtain qualitatively correct results including sharp Kondo resonance exponentially scaling with interaction U. Finally, we present the multi-orbital extension and solve the two-orbital model.